Pneumatic control for compressed-gas circuit breaker having pressurized tank with insulating control tubes pressurized in both the open and closed-circuit positions



:l 12, 1967 w, s JR 3,358,106

PNEUMATIC CONTROL FOR COMPRESSED-GAS CIRCUIT BREAKER HAVING PRESSURIZED TANK WITH INSULATING CONTROL TUBES PRESSURIZED IN BOTH THE OPEN AND CLOSED-CIRCUIT POSITIONS Filed Dec. 7, 1964 4 Sheets-Sheet l Fl (M. I

Dec. 12, 1967 w, s|- JR 3,358,106

PNEUMATIC CONTROL FOR COMPRESSED-GAS CLRCUIT BREAKER HAVING PRESSURIZED TANK WITH INSULATING CONTROL TUBES PRESSURIZED IN BOTH THE OPEN AND CLOSED-CIRCUIT POSITIONS Filed Dec. 7, 1964 4 Sheets-Sheet 2 2i Dec. 12, 1967 w. A. FISH, JR 3,358,106

PNEUMATIC CONTROL FOR COMPRESSED-GAS CIRCUIT BREAKER HAVING PRESSURIZED TANKWITH INSULATING CONTROL TUBES PRESSURIZED IN BOTH THE OPEN AND CLOSED-CIRCUIT POSITIONS Filed Dec. 7, 1964 4 Sheets-Sheet 5 INSULATION CLOSE CIRCUIT TRIP CIRCUIT FIG-2B- Dec. 12, 1967 w. A. FISH, JR 3,35

PNEUMATIC CONTROL FOR COMPRESSEDGAS CIRCUIT BREAKER HAVING PRESSURIZED TANK WITH INSULATING CONTROL TUBES PRESSURIZED IN BOTH THE OPEN AND CLOSED-CIRCUIT POSITIONS Filed Dec. '7, 1964 4 Sheets-Sheet 4 FIGB.

III Q EXHAUST CHAMBER RE EXTERNAL MAIN AND INTERRUPTER MAIN INTERRU IIO I 85 74 AUX- EXHAUST VALVE ISOLATOR EXHAUST VALVE CLOSE United States Patent ABSTRACT OF THE DISCLOSURE A compressed-gas circuit interrupter of the pressurized tank type has arcing contacts and serially-related disconnecting contacts both piston actuated. A three-way air-pilot-operated normally closed first valve has a tank connection to the closing side of the piston for the disconnecting contact under de-energized conditions. A twoway air-pilot-operated normally open second valve controls the pilot section of the first valve and is operated by a three-way normally open close valve externally of the tank structure. An auxiliary switch is controlled by a three-way air-pilot-operated normally-closed valve externally of the tank structure having an exhaust connection to the auxiliary switch cylinder in the de-energized condition. Check valves control the states of operation of the first valve and the last-mentioned valve so that insulating control lines within the tank structure are pressurized in the open and closed-circuit positions of the breaker.

This invention relates, generally, to circuit breakers, and more particularly, to an improved pneumatic control for a circuit breaker having an interrupting unit and a serially-related disconnecting switch unit.

Prior compressed-air circuit breakers of the type described in a copending applicaiton Serial No. 59,882, filed October 3, 1960, now US. Patent 3,214,540, issued October 26, 1965, and assigned to the Westinghouse Electric Corporation, are operated by pneumatic cylinders disposed inside the breaker reservoir and attached directly to individual interrupters and contact members. The operating cylinders are controlled by pressurizing or exhausting them in the proper sequence through insulating tubes. Previous control schemes require some of the insulating tubes to remain exhausted to atmospheric pressure with the contact members of the circuit breaker in either the open or the closed-circuit position. The column of air in each tube at atmospheric pressure between energized and grounded portions of the circuit breaker has worse insulating properties than the surounding high-pressure air, thereby-limiting the surge or impulse voltage the circuit breaker can withstand without fiashover. Furthermore, the control units utilized in previous schemes are complicated and expensive to manufacture and maintain.

An object of this invention is to provide a control system for a compressed-gas circuit breaker in which the insulating control tubes which extend between energized and grounded portions of the circuit breaker are exhausted only momentarily to initiate the opening or closing operations, and are kept at reservoir pressure during both open and closed positions of the contact members of the circuit breaker.

Another object of the invention is to provide for utilizing standard, commercially-available valve units for controlling the operation of a compressed-gas circuit breaker.

A further object of the invention is to provide for keeping the isolating contact members of a compressed-gas circuit breaker open while the reservoir of the breaker is being repressurized after a loss of pressure in the reservoir.

Another object of the invention is to provide an improved pneumatic control for a circuit breaker of the type having an interrupting unit and a serially-related disconnecting switch unit.

Another object is to provide a simplified type of control for a circuit breaker having a series disconnecting switch.

Other objects of the invention will be explained fully hereinafter, or will be apparent to those skilled in the art.

In accordance with one embodiment of the invention, the operation of a compressed-air circuit breaker is controlled by standard, commercial, solenoid-operated and air-pilot-operated valves, which are so connected that insulating control tubes extending between energized and grounded portions of the breaker are under pressure except during the opening and the closing operations of the breaker. The characteristics of the air-pilotoperated valves are such that the isolating contacts of the breaker are kept open while the reservoir of the breaker is being repressurized after a loss of pressure in the reservoir.

For a better understanding of the nature and objects of the invention, reference may be had to the following detailed description, taken in conjunction with the accompanying drawings, in which:

FIGURE 1 is a view, partly in end elevation and partly in section, of a compressed-gas circuit breaker embodying principal features of the invention;

FIGS. 2A and 2B constitute a diagrammatic view of the control system for the circuit breaker, the contact members of the breaker being in the closed position; and,

FIG. 3 is a diagrammatic View of the control system with thecircuit breaker in the open-circuit position.

Referring to the drawings, and more particularly to FIG. 1, the circuit breaker 1 shown therein may be of the type described in the aforesaid patent 3,214,540. The circuit breaker 1 may be of a three-phase type having three pole units, only one of which is shown in the drawing, disposed in a generally cylindrical pressurized metallic tank 2, which is supported by feet 3. The tank 2 is grounded for safety reasons. An arc-extinguishing gas, such as air, is retained within the tank 2 under pressure, for example-250 p.s.i. Other arc-extinguishing gases, such as sulfur hexafiuoride (SP gas may be utilized if desired, it merely being necessary to collect the exhaust gases for subsequent compression and further reuse.

Terminal bushings 4 extend downwardly through supporting sleeves 5 on the upper portion of the tank 2. Each terminal bushing contains a hollow exhaust conductor (not shown) which carries current into the pressurized tank 2 to be interrupted by arc-extinguishing assemblages 6 disposed inside the tank 2. In the present structure, the terminal conductors, which are inside the terminal bushings 4, are hollow, thereby serving to carry the exhaust arced gases out of the tank 2 following a circuit interruption.

As shown in FIG. 1, an inspection door 7 is mounted at one side of the tank 2. A control housing 8 is mounted at the other side of the tank Current transformers 9 encircle the terminal bushings 4. Secondary wiring from the current transformers 9 extends through a conduit 10 to the control housing 8.

As shown in FIGS. 2A and 2B, each arc-extinguishing assembly 6 includes a separable pair of main contacts 11, a pair of maininterrupting contacts 12, and a pair of resistance or impedance interrupting contacts 13. Each arc-extinguishing assembly 6 is supported by an exhaust chamber 14, preferably of cast-metal construction, which is secured to the lower end of one of the terminal bushseries with the resistance contacts 13 and serves to facili tate the interruption of the current through the main interrupting contacts 12. As well known in the art, the insertion of the impedance into the circuit during a portion of the interrupting operation reduces the magnitude of the current to be interrupted and improves the power factor enabling thereby faster interruption.

The interruption of the resistance current by the resistance contacts or resistance interrupter 13 completely interrupts the passage of current through the arc-extinguishing assembly 6. After the interruption of the current, it is desirable to open a pair of isolating, or disconnecting contacts 16, which, as shown in FIG. 1, connect the two arc-extinguishing assemblies 6 in series relation. As shown in FIG. 1, the isolating or disconnecting contacts 16 engage in the closed-circuit position, as at the point 17, and they are separated apart at the end of the opening operation.

By providing the isolating contacts 16, which maintain the circuit open, reclosure of the main contacts 11, the main arcing contacts 12 and the resistance contacts 13 may then be efiected. Since the interior region 18 of the tank 2 contains gas at a relatively high pressure, it is obvious that the disconnecting gaps 17 for the different pole-units are provided in a high-dielectric-strength atmosphere and, consequently, only a minimum disconnecting gap distance need be provided between the separated disconnecting contacts 16. Therefore, the circuit breaker may be reclosed in a relatively short time, by mere reclosure of the disconnecting contacts 16.

During an interrupting operation the main contacts 11 are separated first, then the main interrupting contacts 12 are separated, and then the resistance contacts 13 are separated. After the separation of the resistance contacts the isolating contacts 16 are separated from each other, after which the contacts 11, 12 and 13 are re-closed. The circuit is maintained open by the separated disconnecting or isolating contacts ,16. Thus, as mentioned, the circuit breaker may be reclosed by merely effecting reengagement of the separated isolating contacts 16.

Referring to FIG. 2B, it will be seen that the arcextinguishing gas for interrupting current flow between a relatively stationary orifice contact 19 and a movable main arcing contact 20 of the main interrupting contacts 12 is exhausted operatively through a cup-shaped contact support 21 and into the interior 22 of the exhaust housing 14. To facilitate centering of the main-current are drawn through the orifice contact 19, and the receiving of a radial inward blast of gas, an arc-centering horn 23 is provided. The are horn 23 is perforated and is positioned by a supporting arm 24, which is fastened by bolts 25 to a shoulder portion of the contact support 21. An opening 26 registers with the opening through the contact support 21, and, as previously mentioned, the region 22 within the exhaust housing 14 communicates With the hollow terminal stud, or conductor extending through the associated terminal bushing 4. Thus, the gas blast is exhausted to atmosphere externally of the tank structure 2.

Similarly, a relatively stationary orifice contact 27 and a relatively movable resistance contact 28 are separated to draw a resistance-current are, which is subjected to a gas blast from the region 18 interiorly of the tank 2, through the orifice opening 27a and out through an opening 29 to the region 22 within the exhaust chamber 14. The gas blast is exhausted through the hollow terminal bushing 4 to atmosphere, as previously explained.

As shown in FIG. 2B, the main-current contacts 11 include a plurality of inwardly-extending contact fingers 31 which engage a movable main contact member 32. The contact fingers 31 are attached to the lower wall of the exhaust housing 14. The movable contact member 32 is biased upwardly by compression springs 33. The movable contact member 32 is attached by means of a piston rod 34 and a spacing sleeve 35 to a piston 36 operated vertically within an operating cylinder 37. As will be 4 described more fully hereinafter, exhausting of the gas pressure below the piston 36 will effect downward opening movement of the piston 36 and thereby of the movable contact member 32. This will force the current passing through the main contacts 11 to how by means of the main interrupting contacts 12 and the resistance interrupting contacts 13, although the latter will carry a relatively small proportion of the current because of the presence of the series resistance 15.

The main movable arcing contact member 20 is moved downwardly by a piston 38 movable within an operating cylinder 39 and biased upwardly in a closing direction by a compression spring 40. When air is exhausted from below the piston 38 the pressure of the air within the tank 2 on the piston 38 forces the piston 38 downwardly against the compression of the spring 40. The lower end of a downwardly extending portion 41 of the contact member 29, which is secured to the piston 38, has a reduced spindle-valve portion 42 and a lower enlarged valvespool portion 43. As a result, the valve portions 42 and 43 form a sleeve valve, which prevents or permits communication between a passageway 44 and a passageway 45 leading to the region below a piston 46 of the impedance interrupting unit 13. The passageway 45 is connected to a passageway 47 in a cylinder head 48 of the interrupter 13 by means of an insulating tube 49.

The movable contact member 28 of the resistance interrupter 13 is carried by the piston 46, which operates within a cylinder 51. The piston 46 is biased upwardly by a compression spring 52 disposed between a piston head 53 and a cylinder head or body 48. When air is exhausted from below the piston 46, the pressure of the air within the tank 2 on the piston head 53 forces the piston 46 downwardly against the compression of the spring 52, thereby drawing a resistance-current are, which is extinguished by a gas blast through the orifice opening 27a.

The isolating or disconnecting switch structure, which is designated generally by the reference numeral 55, includes the disconnecting contact member 16, which is actuated by pressure difierences across a piston 56 movable within an operating cylinder 57. Relatively stationary contact fingers 58 bear upon the sides of the movable disconnecting contact 16 to transmit current therethrough from a cylinder head 59, the latter being electrically connected to the resistor 15. The cylinder head 59 is electrically and mechanically connected to a conducting support plate 61 by bolts 62, which extend through feet 63 on the cylinder head 59. The resistor 15 is connected to the support plate 61 by a conductor 64. The plate 61 is connected to the main interrupter unit 12 by means of a conductor 65. The support plate 61 may be mechanically attached to the exhaust chamber 14 by insulating support members 66, only one of which is shown in FIG. 1.

In the closed-circuit position of the breaker 1, as shown in FIG. 1, the current path extends through the hollow terminal conductors enclosed by the terminal bushings 4, the exhaust housings 14 and through the closed contacts 11, 12 and 13 to the conducting support plate 61. The current path then extends through the disconnecting contact structures 55, which are serially connected by the contact members 16 joined at the point 17.

A main exhaust valve 71 is mounted in the lower wall of the tank 2, and an auxiliary exhaust valve 72 is mounted inside the tank, preferably upon the supporting plate 61. As shown most clearly in FIG. 2A, the main exhaust valve 71 includes a manifold 73 which is connected to the passageway 44 of the interrupter 11 by means of an insulating tube 74. As indicated in FIG. 2A, a second tube 74 is connected to the main interrupter unit 11 of the adjacent arc-extinguishing assembly 6. In this manner simultaneous operation of the serially-related arc-extinguishing assemblages 6 is obtained.

An inlet valve 75 controls an opening 76 leading to the interior 18 of th tank structure 2. The inlet valve 75 has a valve stem 80, which is attached to an operating piston 77 movable within an operating cylinder 78. Exhaust passages 79 connect the area above the piston 77 to atmosphere. When the piston 77 is in its uppermost position where it engages a gasket 81, as shown in FIG. 2A, openings 82 in the gasket 81 are closed by the piston 77, thereby preventing the escape'ment of gas through the exhaust passages 79 to atmosphere. To efiect upward motion of the valve stem 80 and consequent opening of the inlet opening 76, high-pressure gas may be supplied to the lower surface of. the piston 77 through a control pipe 83 which is connected to a trip valve 84. The operation of the trip valve 84 will be described more fully hereinafter.

When the high-pressure gas is permitted to exhaust through the trip valve 84, the high-pressure gas inside the tank 2 acting on the top surface of piston 77 moves the piston 77 downwardly to close valve 75 and open the exhaustpassages 79 to atmosphere and permit gas to escape from the arc-extinguishing assemblies 6 through the exhaust tubes 74.

. The auxiliary exhaust valve 72 may be provided as an optional feature to obtain faster opening of the interrupter units 11, 12 aand 13. However, this auxiliary exhaust valve 72 is not necessary in the improved pneumatic control of the instant invention. When the exhaust valve 72 is open, an auxiliary exhaust line extends from the chamber 44 through a pipe 85, the valve 72 and a pipe 86 to the exhaust chamber 22. The chamber 87a above a piston 87 of the exhaust valve 72 is connected to a passageway 88within the resistor interrupter13 by means of a pipe 89. Thus, tank pressure within tank 2 is applied to the top surface of the piston 87 except while the resistor interrupter 13 is open The chamber 87b below the piston 87 is connected to the exhaust line 74 running from the main interrupter unit 11 to the main exhaust valve 71. Thus, tank pressure is also applied to the lower surface of the piston 87 except while the operating cylinders 37, 39 in the main interrupter unit 11, 12 are being exhausted.

When the exhaust line 74, is open to atmosphere, the pressure differential drives the piston 87 downwardly, thereby opening a valve member 91. This valve 91 opcrates at approximately the same pressure differential as the external main contacts 31, 32 and provides faster opening of themain and the resistor interrupters 12, 13. When the resistor interrupter 13 opens, exhausting the chamber above the piston 87, the valve 91 is reclosed by a spring 92. Readmission of pressure to the lower side of the piston 87, when the interrupters are reclosed, seals the valve 91 in the closed position until the next opening operation.

From th foregoing description, it will be seen that the interrupter units 11,. 12, 13 and the isolating switch 55 are operated by pneumatic cylinders inside the breaker reservoir and attached directly" to the individual interrupters and contacts. The operating cylinders are controlledby pressurizing or exhausting them in the proper sequence through insulating tubes. Previous control schemes required some of the insulating tubes to remain exhausted to atmospheri pressure whenthe; circuit breaker is in the open or the closed-circuit position. The resulting column of air at atmospheric pressure between live, or energized and grounded portions of the circuit breaker has poorer insulating-qualities than the surrounding high-pressure air withinregion 18 and thus limits the surge, or impulse voltage the circuitv breaker 1 can Withstand without flashover. I .Furthermore, prior control schemes required the provision of somewhat complicated and expensive control valves-The control valves utilized in the present system however, are standard, commercially-available valves.

Also, the valvesare so connected in the control system that the insulating control tubes from energized to grounded portions of the circuit breaker 1 are exhausted only momentarily to initiate the opening and the closing operations, and they remain at reservoir pressure during both open and closed positions of the circuit breaker 1. This eliminates the column of low-pressure air during the time the circuit breaker is standing open or closed and exposed to surge or impulse voltage. The high-pressure control tubes are shown speckled in the drawing, thereby indicating high-pressure condition-s therein.

As shown in FIG. 2A, the trip valve 84 is a standard, commercially-available, solenoid-operated, three-way, normally-open air valve. Likewise, a closing valve 94 is of the same type and construction as the trip valve 84. Control valves A and Dare standard, commercially-available, air-pilot-operated, three-way, normally-closed air valves with an internal bleeder connection, indicated by the dotted lines a and d, respectively, between the pilot sec tion and the outlet of each valve A and D. Control valves' B and E are standard, commercially-available, air-pilotoperated, straight-way, normally-open air valves. Valves C, F and H are standard, commercially-available check valves. One each of valves A, B and C is required for each interrupter assembly 6. One each of the close and the trip valves 94, 84 and valves D, E, F and H is required per circuit breaker 1. A control tube 95 extending from the check valve F in the control housing 8 to the interrupter 6 is required for one interrupter only.

For purposes of this application, a normally open valve is one which passes fluid from an inlet to an outlet when the actuating coil, or the pilot section, is deenergized or depressurized. A normally closed valve is one which passes fluid when the actuating coil, or the pilot section, is energized, or pressurized.

The tank reservoir 18 is filled with high-pressure air, or other interrupting gas, through a valve 96 and a supply pipe line 97. The check valve H maintains the reservoir 18 and the pipe line 97 at high pressure unless drained through a drain valve 98.

As shown in FIGS. 2A and 2B, the circuit breaker 1 is in the closed-circuit position. Energizing the solenoid 101 of the trip valve 84 through a conductor 102, which is connected to any conventional tripping circuit, through contact members 103 of an auxiliary switch 104, closes the trip valve 84 and exhausts the tube 83 leading to the main exhaust valve 71, thereby exhausting the control tubes 74 leading to the interrupters 6 and causing the external mains 11, the main interrupters 12, and the resistor interrupters 13 to open in sequence and interrupt the current through 'the circuit breaker, as generally set forth in the aforesaid Patent 3,214,540. The sequential operation of the interrupters 11, 12 and 13 is obtained by means of slide valves 105, 106 and 107 in the interrupter units 11, 12 and 13, respectively, in the manner fully described in the aforesaid patent.

The opening of the resistor interrupter 13 permits the pilot sections of valves A and D to be exhausted through check valves C and F, respectively, and the pipes 89 and 95. Valves A and D will thus move to their normally closed positions as shown in FIG. 3. The closing of valve A exhausts the cylinder 57 of each isolating switch 55 through a pipe line 110, the valve A and a line 111, which is connected to the exhaust chamber 22. This causes the movable disconnecting contact members 16 of the isolating switches 55 to be moved to their open isolating position. The closing of the valve D exhausts pressure from the operating cylinder 112 of the auxiliary switch 104, thereby opening the contact members 103 and closing contact members 113 of the auxiliary switch 104.

The trip valve solenoid 101 is deenergized by the auxiliary switch operation 104, permitting the trip valve 84 to return to its normally-open position. This recloses the main exhaust valve 71.and the auxiliary exhaust valve 72, thereby admitting pressure to the control tubes 74 leading to the interrupting assemblies 6 and permitting the interrupters 11, 12 and 13 to reclose. Reclosing the resistor interrupter 13 readmits pressure to the tubes 89, 95 leading to check valves C and F; however, the check valves C and F prevent air flow to the pilot sections of valves D and A. The isolator cylinders 57 and the auxiliary-switch operating cylinder 112 thus remain exhausted, maintaining the breaker open position. Any minor leakage, which would tend to repressurize the pilot sections of valves A and D and cause premature operation, is drained through the internal bleeder connections a, d to the outlet and exhausted through the exhaust ports of the valves A and D. The circuit breaker 1 is then in the open-circuit position, as shown in FIG. 3 of the drawlngs.

The closing operation of the circuit breaker 1 is initiated-by energizing the solenoid 114 of the close valve 94 through a conductor 115 and the contact members 113 of the auxiliary switch 104. Energizing the solenoid 114 closes the close valve 94, thereby exhausting the pilot sections of the valves B and E, which are connected to the closing valve 94 through an insulating control tube 116. Valves B and E will thus move to their normallyopen position, admitting pressure to the pilot sections of valves A and D. This opens valves A and D admitting pressure to the isolator cylinder 57 and the auxiliary switch operating cylinder 112 and causing the pistons in them to move to the breaker closed position. Since the valves A and B are located inside the pressurized tank 2 they receive high-pressure air from the tank 2. The closing valve solenoid 114 is deenergized by the operation of the auxiliary switch 104 in opening the contacts 113, thereby reclosing valves B and E and leaving the circuit breaker 1 closed, as shown in FIGS. 2A and 2B, and ready for another tripping operation.

It is standard practice on compressed-air circuit breakers to provide low-pressure switches to trip the breaker and open the closing circuit, so that the closing valve cannot be energized in the event the air pressure drops below a safe operating pressure. Therefore, the circuit breaker will always be open when air pressure is drained from the reservoir. The operating characteristics of valves A, B, D and E can be such that valves B and B will operate at a pressure lower than that at which valves A and D will operate. This assures that valves B and B will remain closed until the pressure has dropped too low to operate valves A and D, thereby maintaining the circuit breaker 1 in the open position. When the reservoir 2 is refilled, valves B and B will reclose before the pressure is high enough to open valves A and D, thereby maintaining the isolator and auxiliary switch operating cylinders 57, 112 and the pilot sections of valves A and D at atmospheric pressure. Therefore, the isolator contacts and the auxiliary switches will always remain in, or moveto the breaker open position as the reservoir 2 is pressurized.

From the foregoing description it is apparent that the invention provides a pneumatic control system for controlling the operation of a compressed-gas circuit breaker which has the following advantages: (1) no tubes extending between live or energized and grounded portions of the circuit breaker 1 are at atmospheric pressure in either the open or the closed position of the contact members of the breaker; therefore, the low-pressure column of air or gas, present in previous control schemes, is eliminated, and the circuit breaker insulation is improved. (2) This scheme utilizes only standard, commercially-available, air or fluid valves for control of the sequence of operations. This-eli-minates'the need for somewhat complicated and costly control units. (3) The operating characteristics of the valves are such that the contact members of the breaker are maintained in the open position as the reservoir is repressurized after a loss of pressure. (4) The present control scheme is simple, compared to previous schemes, and therefore is inherently trouble-free in operation.

Since numerous changes may be made in the above-described construction, and different embodiments of the invention may be made without departing from the spirit and scope thereof, it is intended that all subject matter contained in the foregoing description, or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sen se I claim as my invention: 1. A compressed-gas pressurized-tank type circuit interrupter including a pair of separable arcing contacts (27, 28) and a pair of serially-related disconnecting switch contacts (16, 16) an isolator piston (56) for moving one of said disconnecting switch contacts, a three-waynormally-cl-o'sed first control valve (A) having a gas-o-perated pilot section for pressurizing or exhausting the closing side of said isolator pison, a two-way normally-open 'sec-' said operating pist0n (46), a check-valve-controlled gascontrolling tube (8-9) leading from the closing side of said operating piston (46) to a point intermediate the outlet ofsaid second control valve and the inlet to the gas-operated pilot section of said first control valve, means biasing said one arcing contact to the closed position, means including a three-way close valve (94) for opening said second control valve to thereby pressurizethe pilot section of the first control valve and thus pressurize the closing side of the isolator piston, and a three-way electrically operated trip valve (84) for operating said main exhaust third valve.

2. The combination of claim 1, wherein an auxiliary switch (164) is pneumatically actuated having one side of its piston pneumatically connected to a three-way airpilot-operated fourth valve (D) having its pilot section controlled by a two-way air-pilot-operated fifth valve (E) pneumatically'connected to the close valve (94).

3. The combination of claim 2, wherein a pneumatic connection to the piston (46) is check-vlave-contr-olled to the outlet of the fifth valve (E).

4. The combination of claim 1, wherein the first control valve (A) has a bleeder connection (a) from its pilot section to its outlet. 7

5. The combination of claim 14, wherein valve (B) operates at a lower pressure than valve (A).

6. The combinationof claim 1, wherein valve (B) opcrates at a lower pressure than valve (A).

7. The combination of claim 2, wherein valves'(B); and (E) operate at a lower pressure than valves (A) and 8. The combination of claim 2, wherein valves (A) and (D) have respective bleeder connections (a), (d) leading from their pilot sections to their outlets.

9. The combination ofclaim 14, wherein a resistance is in series with the contacts (27, 28) and apair of arcing contacts (19, 20) in parallel with said contacts (27,28)

are pneumatically actuated first in sequence by said main exhaust third valve (71). a

10. The combination of claim 1, wherein a resistance is in series with the contacts (27, 28) and a pair of arcing contacts (19, 20) in parallel with said contacts (27, 28) are pneumatically actuated first in sequence by said main exhaust third valve (71). I

11. A circuit interrupter'including a pair of separable arcing contacts (27, 28) and 'a pair of' serially-related disconnecting switch contacts (16, 16) and isolator piston" (56) for moving one of said disconnecting switch contacts, a three-way normally-closed first control valve (A) having a gas-operated pilot section for pressurizing or ex-' hausting the closing side of said isolator piston, a two-way normally-open second control valve (B) for controllingthe pressurizing of the gas-operated pilot section of the said first control valve, an operating piston (46) movable within a cylinder for opening one of said arcing contacts,

a main exhaust third valve (71) for exhausting the opening side of said operating piston (46), a check-valve-controlled gas-control tube (89) leading from the opening Side of Said Operating piston (46) to a point intermediate the outlet of said second control valve and the inlet to the gas-operated pilot section of said first control valve, means biasing said one arcing contact to a closed position, and means for opening said second control valve to thereby pressurize the pilot section of the first control valve and thus pressurize the closing side of the isolator piston.

12. The combination according to claim 11, wherein the second control valve (B) has a gas-operated pilot section, and a three-way normally-open closing valve pressurizes and exhausts the last-mentioned pilot section.

13. The combination according to claim 11, wherein an auxiliary switch is provided having a piston operable within a cylinder, and a three-way normally-closed fourth control valve supplies the opening end of said cylinder for the auxiliary switch.

14. A circuit interrupter including a pair of separable arcing contacts (27, 28) and a pair of serially-related disconnecting switch contacts (16, 16), an isolator piston (56) for moving one of said disconnecting switch contacts, a three-way normally-closed first control valve (A) having a gas-operated pilot section for pressurizing or exhausting the closing side of said isolator piston, a two-way normally-open second control valve (B) for controlling the pressurizing of the gas-operated pilot section of the said first control valve, an operating piston (46) movable within a cylinder for opening one of said arcing contacts, a main exhaust third valve (71) for exhausting the opening side of said operating piston (46), a check-valvecontrolled gas-controlled tube (89) leading from the opening side of said operating piston (46) to a point intermediate the outlet of said second control valve and the inlet to the gas-operated pilot section of said first control valve, means biasing said one arcing contact to the closed position, means for opening said second control valve to thereby pressurize the pilot section of the first control valve and thus pressurize the closing side of the isolator piston, an auxiliary switch having a piston operable within a cylinder, a three-way normally-closed fourth control valve supplying the opening end of said cylinder for the auxiliary switch, the fourth control valve having a gas-operated pilot section, and a two-way normally-open fifth control valve utilized to pressurize and exhaust the last-mentioned pilot section.

15. The combination according to claim 14, wherein a check-valve-controlled gas-controlled tube leads from the opening side of the operating piston (94) to a point intermediate the outlet of said fifth control valve and the inlet to the gas-operated pilot section of said fourth control valve.

References Cited UNITED STATES PATENTS 2,783,338 2/1957 Beatty 200-148 3,214,540 10/1965 Schrameck et a1 200148 3,244,844 4/ 1966 Forwald 200-148 3,311,726 3/1967 Fish 200148 ROBERT S. MACON, Primary Examiner. 

1. A COMPRESSED-GAS PRESSURIZED-TANK CIRCUIT INTERRUPTER INCLUDING A PAIR OF SEPARABLE ARCING CONTACTS (27,28) AND A PAIR OF SERIALLY-RELATED DISCONNECTING SWITCH CONTACTS (16,16) AN ISOLATOR PISTON (56) FOR MOVING ONE OF SAID DISCONNECTING SWITCH CONTACTS, A THREE-WAY NORMALLY-CLOSED FIRST CONTROL VALVE (A) HAVING A GAS-OPERATED PILOT SECTION FOR PRESSURIZING OR EXHAUSTING THE CLOSING SIDE OF SAID ISOLATOR PISON, A TWO-WAY NORMALLY-OPEN SECOND CONTROL VALVE (B) FOR CONTROLLING THE PRESSURIZING OF THE GAS-OPERATED PILOT SECTION OF THE SAID FIRST CONTROL VALVE, SAID TWO VALVES BEING WITHIN THE PRESSURIZED TANK ADJACENT THE DISCONNECTING SWITCH CONTACTS, AN OPERATING PISTON (46) MOVABLE WITHIN A CYLINDER FOR OPENING ONE OF SAID ARCING CONTACTS, A MAIN EXHAUST THIRD VALVE (71) DISPOSED ADJACENT THE TANK WALL FOR EXHAUSTING THE OPENING SIDE OF SAID OPERATING PISTON (46), A CHECK-VALVE-CONTROLLED GASCONTROLLING TUBE (89) LEADING FROM THE CLOSING SIDE OF SAID OPERATING PISTON (46) TO A POINT INTERMEDIATE THE OUTLET OF SAID SECOND CONTROL VALVE AND INLET TO THE GAS-OPERATED PILOT SECTION OF SAID FIRST CONTROL VALVE, MEANS BIASING SAID ONE ARCING CONTACT TO THE CLOSED POSITION, MEANS INCLUDING 